patch 8.1.1347: fractional scroll position not restored after closing window

Problem:    Fractional scroll position not restored after closing window.
Solution:   Do restore fraction if topline is not one.

Author: brammool

src/testdir/test_window_cmd.vim

@@ -745,16 +745,8 @@ endfunc
 
 func Test_split_noscroll()
   let so_save = &so
-  new
-  only
-
-  " Make sure windows can hold all content after split.
-  for i in range(1, 20)
-    wincmd +
-    redraw!
-  endfor
-
-  call setline (1, range(1, 8))
+  enew
+  call setline(1, range(1, 8))
   normal 100%
   split
 
@@ -769,12 +761,20 @@ func Test_split_noscroll()
   call assert_equal(1, info1.topline)
   call assert_equal(1, info2.topline)
 
-  " Restore original state.
-  for i in range(1, 20)
-    wincmd -
-    redraw!
-  endfor
+  " window that fits all lines by itself, but not when split: closing other
+  " window should restore fraction.
   only!
+  call setline(1, range(1, &lines - 10))
+  exe &lines / 4
+  let winid1 = win_getid()
+  let info1 = getwininfo(winid1)[0]
+  call assert_equal(1, info1.topline)
+  new
+  redraw
+  close
+  let info1 = getwininfo(winid1)[0]
+  call assert_equal(1, info1.topline)
+
   bwipe!
   let &so = so_save
 endfunc

src/version.c

@@ -767,6 +767,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1347,
 /**/
     1346,
 /**/

src/window.c

@@ -5830,10 +5830,11 @@ scroll_to_fraction(win_T *wp, int prev_height)
     // Don't change w_topline in any of these cases:
     // - window height is 0
     // - 'scrollbind' is set and this isn't the current window
-    // - window height is sufficient to display the whole buffer
+    // - window height is sufficient to display the whole buffer and first line
+    //   is visible.
     if (height > 0
         && (!wp->w_p_scb || wp == curwin)
-        && (height < wp->w_buffer->b_ml.ml_line_count))
+        && (height < wp->w_buffer->b_ml.ml_line_count || wp->w_topline > 1))
     {
 	/*
 	 * Find a value for w_topline that shows the cursor at the same